B11 Flashcards
Vision condition in which a person can not align both eyes simultaneously under normal conditions
Strabismus
Causes of Strabismus?
1) Congenital
2) accom ET
3) abnormal visual development
4) Neurological
Important questions to ask:
1) Onset?
2) Head trauma?
3) perinatal hx?
4) other neurological signs?
5) old photos?
6) head tilt?
Types of Neurological strabs:
- CN 3, 4, 6 palsies
- neuro diseases (myasthenia gravis, botulism)
- post fossa tumors or malformations (Arnold Chiari)
- raised intracranial pressure (hydrocephalus, idiopathic, tumor)
Strab symptoms:
- diplopia
- blurred vision
- reduction in peripheral vision
- headaches
- dizziness
Oculomotor Nerve Palsy (CN 3)
Muscles/anatomical structures innervated:
SR, MR, IR, IO, sup palpebral levator muscle, Edinger-Westphal nucleus
Eye/head position seen in CN 3 palsy
Down & Out
ptosis, dilated pupil with no accom resp
Etiology of CN3 palsy in children
Congenital
Vascular (AV malformations)
Primary tumor
Metastatic tumor
Etiology of CN3 palsy in young adults
Demyelinating
Vascular (hemorrhagic or infarction)
Tumor
Etiology of CN3 palsy in older adults
Vascular (infarct)
Tumor
Ischemic/Vascular CN 3 palsy causes
Diabetes
Hypertension
Pupil sparing
Compressing (non-pupil sparing) CN 3 palsy causes
Intracranial aneurysm
- most common sites: Post comm a., ICA, basilar a.
- risk of rupture causing Subarachnoid heme
Neoplasm
- primary tumors: neuromas, schwannomas
- tumors adjacent to nerve: pituitary, sphenoid wing meningioma
Trauma CN 3 palsy causes
Severe blows to head w skull fracture and/or loss of consciousness
Migraine CN 3 palsy causes
Ophthalmoplegic migraine ->from recurrent demyelinating neuropathy?
( can be seen in children & young adults)
Inflammatory CN 3 palsy causes
MS
Infection CN 3 palsy causes
Meningitis
Viral
Tests to eval CN 3 palsy
1) Case hx: diplopia? Decr vision at near? Onset? Trauma?
2) external observation
3) VA
4) CT
5) EOMs
6) pupils
7) NPC
8) accom testing
9) Hess-Lancaster test
Trochlear Nerve Palsy (CN 4)
Muscles/ anatomical structures innervated:
SO
Eye/head position in CN4 palsy:
Up & In
Compensatory head TILT to OPPOSITE side of palsy (ex: R head tilt = LSO palsy)
CN4 pathway
(Longest intracranial pathway & fx is purely somatic motor)
- exits posteriorly from midbrain & crosses one another
- partially encircling the midbrain
- decussates after midbrain
- runs anteriorly & inferior w/in subarachnoid space before piercing the dura mater adjacent to post clinoid process of sphenoid bone
- Nerve travels along lateral wall of cavernous sinus (beside CNIII, CNVI, V1 & V2, & ICA) before entering orbit
- enters orbit via Sup orbital fissure
- innervated only the Sup Oblique m. of each eye
CN 4 Palsy symptoms:
- Vertical diplopia, exacerbated when looking down & in (such as reading or walking down stairs)
- head tilt away from affected side
CN 4 is near the descending sympathetic fibers, thus what can also be present during a CN 4 palsy?
Ipisilateral pre-gang. Horner’s Syndrome
Horner’s syndrome triad: miosis, ptosis, anhydrosis
Etiologies of CN4 palsy
Congenital
- abnormal development of CN4 nucleus
- abnormal development of peripheral nerve or tendon
Acquired
- idiopathic (#1)
- head trauma w/ loss of consciousness (#2)
- microvasculopathy (DM, atherosclerosis, HTN)
Others:
- tumor
- aneurysm
- MS
- Iatrogenic injury
Test used to eval CN 4 palsy
- Case hx: vertical diplopia? Difficulty reading? Sense of things are tilted?
- external obs
- CT
- EOMs
- pupils
- Parks 3 Step
- NPC
- Hess-Lancaster
Abducens Nerve Palsy (CN6)
CN 6 innervated what muscles/anatomical structures?
LR
Eye/head position seen in CN 6 palsy
IN
Compensatory head TURN TOWARD affected eye
CN ____ has a long external course through cranium making it susceptible to _____________(list 5)
6; injury, incr ICP, mastoid infection, skull fracture, tumors
Lesion of nerve, root, or nucleus of CN6 presents as
- ipsilateral paresis of LR
- convergent strabismus incr in temporal gaze
- lateral diplopia
- ipsilateral paresis of facial muscles (for nuclear lesions) (CN7 encircles CN6 n.)
Most commonly affected oculomotor n. in adults & 2nd most common in children
CN6
Muscle more affected by ischemia than other EOMs
LR
